Conventionally, there has been known a power generation equipment such as a photovoltaic cell (PV) or a solid oxide fuel cell (SOFC). Also known is a system of controlling an interconnection between a power generation equipment and a power grid (hereinafter, Energy Management System (EMS)). The EMS controls such that power supplied by the power generation equipment is output to a power grid (reverse power flow control), and so forth (for example, Patent Literature 1).
However, for example, in a case in which a large number of power generation equipment are connected to a power grid, when power is output to the power grid from the large number of power generation equipment, the voltage value of the power grid is increased. When the voltage value of the power grid reaches an allowable voltage value, the power output from the power generation equipment to the power grid (reverse flow power) is suppressed so that power is not output to the power grid in a state in which a voltage value of the power grid exceeds an allowable voltage value that is allowable in the power grid.
As described above, when the voltage value of the power grid reaches the allowable voltage value, the power output from the power generation equipment to the power grid (reverse flow power) is suppressed.
In such a case, it is necessary to reduce the power generated by the power generation equipment. However, it is assumed that there is a case in which the power generation capability of the power generation equipment is not sufficiently utilized. For example, in a case in which the power generation equipment is equipment that generates power by using natural energy, the use efficiency of the natural energy declines. Further, in a case in which a following capability of the amount of generated power is not excellent, the power generated by the power generation equipment is wasted.